I genuinely think that anyone offended by it is quite simply either a bit ignorant or a bigot.
I genuinely don't know how many more times or how many more ways I can say this: I AM A WOMAN.
WOMAN
It is what I AM.
I needs no clarification as it describes 1 aspect of WHO I AM! It has done so for millenia and will do so for many more.
A man who chooses to identify as a woman IS NOT A WOMAN. They are TRANS WOMEN. And I have absololutely no issue with that, if that is the label they choose to describe themselves. They cannot be WOMAN, as they are not, by biology, by social construct, etc.
I CHOOSE to be OFFENDED by the term cis as it imposes a label on me that has absolutely nothing to do with me. It is a construct placed upon me and my identity by one cohort of society which has chosen, unilaterally, to make me and other WOMEN a subset of WOMEN instead of simply being WOMEN.
If the term cis, or any other term is to be used then WOMEN should be involved in that decision. Currently, here on MN, there are any number of WOMEN who, like myself, say "No thanks, I don't want a new label, I am happy with the one I have".
Ignorance is to ignore my protest at being relabelled, renamed. Bigotry is to deny my voice on the matter.